The invention relates to a method for operating a drive train of a motor vehicle including an oil pump driven by an electric motor for supplying pressurized oil for operating shifting elements, and also to a drive train arrangement of a motor vehicle.
DE 101 60 466 C1 discloses a drive train in which an oil pump supplies a hydraulically shifted transmission unit with pressurized oil. The oil pump can be driven by two devices, an internal combustion engine or an electric motor. At any time, the device with the higher speed is coupled to the oil pump. If the speed of the internal combustion engine is too low for adequate operation of the oil pump, the oil pump is driven by the electric motor. The drive train further includes a first and a second electric motor which, as required, can apply a torque to the transmission input shaft or can be used for starting the internal combustion engine. The second electric motor can also be used for driving with purely electromotive propulsion.
It is the object of the invention to provide for reliable starting of the electric motor for driving the oil pump with high reliability under all operating conditions.